Wankel engine

Top: cutaway of an automobile engine with
automatic transmission, based on the NSU Ro 80 engine. This engine
has two rotors and is mounted longitudinally, forward of the front
(driving) wheels. Above: stages in the working cycle of a
Wankel engine. Actually, each of the three combustion chambers on
each rotor follows its own working cycle of intake, compression, combustion,
and exhaust, at phase angles 120° before and after its fellows.

The Wankel engine is an internal combustion engine that produces rotary motion directly. Invented
by the German engineer Felix Wankel (1902–1988), who completed his first
design in 1954, it became widely used in automobiles and airplanes, and
continues to be used in various forms today. A triangular rotor with spring-loaded
sealing plates at its apexes rotates eccentrically inside a cylinder, while
the three combustion chambers formed between the sides of the rotor and
the walls of the cylinder successively draw in, compress and ignite a fuel-and-air
mixture. The Wankel engine is simpler in principle, more efficient and more
powerful weight for weight, but more difficult to cool, than a conventional
reciprocating engine.